WO1999058006A1

WO1999058006A1 - Cigarette manufacture

Info

Publication number: WO1999058006A1
Application number: PCT/GB1999/001539
Authority: WO
Inventors: Alan Michael Aindow; John Dawson; Kevin Middleton; Charles Simpson
Original assignee: Molins Plc
Priority date: 1998-05-14
Filing date: 1999-05-14
Publication date: 1999-11-18
Also published as: GB9810412D0

Abstract

A laser perforation system includes an electrically driven laser beam deflector (14) which is controlled to cause the beam to be directed in sequence along a number of paths (10A-D) leading to a perforation zone (8). The beam deflector may be an acousto-optical device (14). A frequency modulated control signal may be applied to the beam deflector to cause it to deflect the beam along different paths (10A-D). Switching of the beam by an acousto-optical device produces higher definition pulses than are generally obtainable from a laser pulsed at source or by a mechanical device. The control signals for the beam deflector may be amplitude modulated to vary beam intensity. The target cigarettes (4) may be rotated in the perforation zone (8), so as to receive circumferential rows of perforations from beams on said paths (10A-D).

Description

Cigarette Manufacture

This invention relates to cigarette manufacture, particularly of ventilated cigarettes which have perforations generally in the region of the filter or mouth end of the cigarette.

It is known to produce perforations in the wrappers of complete or nearly-complete cigarettes by means of a focused pulsed laser beam. British patent specification No. 2256572 discloses a system in which a series of laser beam pulses is directed towards cigarettes travelling in substantially parallel paths in a filter cigarette assembly machine, so as to produce at least one row of perforations on each passing cigarette. In this system a laser beam generated by a laser source is directed along predetermined multiple paths towards the cigarettes by reflectors including a plurality of rotary mirrors which are driven in synchronism with the passage of cigarettes through the machine and serve to direct beam pulses along the predetermined paths. The rotary mirrors may have series of reflective and transmissive elements which intercept an incident beam and so generate a series of pulses along said paths.

A somewhat similar arrangement, also involving the use of a rotary beam deflecting unit which is synchronised with the passage of cigarettes, is disclosed in British patent specification No. 2238704. Also disclosed in this arrangement is the use of semi-silvered mirrors or equivalent means for producing multiple beams from a single incident beam by so-called beam splitting.

British patent specification No. 2149644 relates primarily to a system for perforation of a web of cigarette tipping paper, portions of which are subsequently used in a filter cigarette assembly machine to join filters to tobacco rod sections to produce ventilated cigarettes. In this specification, which is hereby incorporated herein in its entirety, there is disclosed a system in which an electrically driven beam deflector is arranged in the path of a laser beam, the deflector having a controllable drive whereby deflection of the beam is controlled to cause the beam to impinge on and perforate a moving component of the cigarette industry (especially but not necessarily cigarette tipping paper). 2

The preferred form of the device is an acousto-optic deflector, by which the beam is deflected either along a predetermined path or to a heat sink. The beam exiting from the deflector along said predetermined path is subsequently directed along multiple paths using a series of mirrors and is subsequently split to produce multiple beams.

According to one aspect of the present invention a method of perforating cigarettes or cigarette components by means of a laser beam comprises directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector and controlling the drive to the deflector to cause the beam to be directed in sequence along a plurality of predetermined paths leading to a perforation zone. Preferably the deflected beams are directed on said predetermined paths to said perforation zone without further impingement on any actively-controlled means. Preferably the drive is controlled so as also to control the intensity of at least one of the beams on said predetermined paths and/or to control the duration of the beam on at least one of said paths. In this sense the term "duration" includes the duration of individual pulses on said path; the term may also refer to the proportion of time during which the deflector directs a beam along the respective path.

In a preferred arrangement the electrically driven beam deflector is an acousto-optical deflector, which preferably directs deflected beams along different predetermined paths in accordance with the frequency of an applied alternating current signal.

According to another aspect of the present invention, a method of perforating cigarettes or cigarette components by means of a laser beam comprises directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector (preferably an acousto-optical device) and controlling the drive to the deflector by application of frequency modulated signals selectively to deflect the beam along at least two predetermined paths. In particular, beam pulses on the paths may be switched by the deflector: acousto- optical devices in particular are capable of generation of high definition pulses having rapid rise and fall times as compared with pulses generated by a laser source or by conventional (mechanical) means. In a preferred arrangement the 3

signals may be amplitude modulated to control the intensity of the beam on at least one of said predetermined paths. In a preferred form of acousto-optical device, application of no control signal (i.e. zero amplitude) results in no resultant deflection (i.e. no resultant angular deflection), but the beam may be displaced by refraction depending on the angle of incidence. Preferably this non-deflected beam is not used for producing perforations and may be directed to a heat sink.

According to a further aspect of the invention a method of perforating cigarettes or cigarette components by means of a laser beam comprises directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector and controlling the drive to the deflector to

(i) produce multiple beams in sequence along predetermined paths, (ii) vary the intensity of a beam on at least one of said paths, and (iii) vary the duration of the beam on at least one of said paths. The invention extends also to apparatus for performing the method according to any one of its aspects. The invention also extends to cigarette perforating apparatus including a common non-mechanical device to achieve the functions of at least any two and preferably three of sub-paragraphs (i)-(iii) above. The invention will be further described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is a schematic view of a cigarette perforation system, Figure 2 is an enlarged detail view of part of the system of Figure 1, and Figure 3 is a plan view of a cigarette being perforated in the system of Figure 1.

An intermediate or drying drum 2 of a filter cigarette assembly machine conveys double length filter cigarette rods 4 in flutes (not shown in the drawing) provided with recesses which allow each cigarette to be rolled backwards relative to the surface of the drum 2 by a counter drum 6 which engages each successive cigarette conveyed by the drum 2 in a perforation zone 8. The arrangement is such that each successive cigarette 4 temporarily remains stationary and rotates about its own axis in the zone 8. Reference is directed to 4

Figures 15 and 16 of British patent specification No. 1602133 for details of a similar system.

Each double length cigarette 4 comprises single length tobacco sections 4A and 4B and a double length filter portion 4C. Downstream of the perforation zone 8 the drum 2 delivers the cigarettes 4 to a downstream part of the filter assembly machine in which each cigarette 4 is divided at its mid-point to provide two individual filter cigarettes. In the zone 8 the filter portion 4C receives two axially-spaced circumferential rows of perforations in positions such that each individual filter cigarette will include a row of perforations around its filter. Typically each cigarette 4 may be rotated through 180° in the zone 8 to receive a complete row of perforations.

The rows of perforations are produced by four pulsed laser beams 10A- D derived from a primary laser beam 10 generated by a laser source 12. The beam 10 is passed through an acousto-optical deflector 14 which is operated to generate each of the beams 10A-D in sequence. As shown in Figure 2, each of the beams 10A-D is deflected by the device 14 along paths which are angularly separated. A zero order beam 10E, corresponding to the path of a non-deflected beam through the deflector 14, is directed to a heat sink or dump 16.

The divergent beams 10A-D are directed towards a primary mirror array 18 from which they are directed to secondary mirror arrays 20 for redirection to the perforation zone 8. It will be appreciated that each of the arrays 18,20 comprises separate mirrors for each of the beams 10A-D so that individual beams may be directed as required.

The deflector 14 comprises an acousto-optical modulator which diffracts a portion of the incident laser beam 10 on application of an alternating current

(radio frequency) signal on the control line 22 (Figure 2). The angle and intensity of the deflected beam are related to the frequency and amplitude of the applied signal. Thus, in the absence of any signal on line 22 the beam 10 is directed along the beam path 10E. By application of a signal of predetermined frequency on control line 22 a portion of the beam 10 is directed along one of the beam paths 10A-D corresponding to the predetermined frequency. By modulating the signal so that it carries in sequence successive portions having 5

predetermined frequencies corresponding to those required to produce deflections corresponding to the respective beams 10A-D it is possible to generate the beams 10A-D in predetermined sequence. By switching of the signal on control line 22 it is possible to produce beam pulses of predetermined length on any of the beam paths 10A-D. In all cases at least a portion of the beam 10 remains directed along the path 10E: this portion may be varied, to vary the intensity of the deflected beams, by controlling the amplitude of the signal applied on line 22.

The signal on control line 22 is provided by a radio frequency driver 24, operation of which is synchronised with the speed of the filter assembly machine and which may also be provided with a feedback signal dependent on measured ventilation of filter cigarettes produced by the machine. Synchronisation and feedback signals are respectively supplied along lines 26, 28. For further details of a typical feedback arrangement for controlling an acousto-optical device reference is directed to said specification No. 2149644.

Note that for the purposes of illustration the angles are exaggerated in Figures 1 and 2: typically with an incident beam at about 2° from normal to the surface of the deflector 14 the angle contained between the beams 10A and 10D is about 2° and the mean angle of deflection (i.e. of the beams 10A-D from the beam 10E) is about 4°.

One form of acousto-optical deflector which may used in the system of Figure 1 is model 1207B-6-BS available from Isomet Corporation of Springfield, Virginia, USA. With this or similar devices and an associated driver it is possible to switch the beams very rapidly, and significantly more quickly than is achievable by pulsed laser sources or by conventional mechanical means

(such as chopping discs). Thus, the deflector 14 is capable of high definition pulse shaping.

A suitable laser source 12 is the Coherent Diamond 84, which is a CO₂ sealed unit providing a pulsed beam having a peak power of 550 watts, available from Coherent, Cambridge, UK.

Claims

6Claims

1. A method of perforating cigarettes or cigarette components by means of a laser beam, comprising directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector and controlling the drive to the deflector to cause the beam to be directed in sequence along a plurality of predetermined paths leading to a perforation zone.

2. A method as claimed in claim 1, wherein the deflected beams are directed on said predetermined paths to said perforation zone without further impingement on any actively-controlled means.

3. A method as claimed in claim 1 or 2, wherein the drive is controlled so as also to control the intensity of at least one of the beams on said predetermined paths .

4. A method as claimed in any preceding claim, wherein the drive is controlled so as to control the duration of the beam on at least one of said paths.

5. A method as claimed in any preceding claim, wherein the electrically driven beam deflector is an acousto-optical device arranged to direct deflected beams along different predetermined paths in accordance with the frequency of an applied alternating current signal.

6. A method of perforating cigarettes or cigarette components by means of a laser beam, comprising directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector and controlling the drive to the deflector by application of frequency modulated signals selectively to deflect the beam along at least two predetermined paths. 7

7. A method as claimed in claim 6, including the step of switching beam pulses on said paths.

8. A method as claimed in claim 6 or 7, wherein the signals are amplitude modulated to control the intensity of the beam on at least one of said predetermined paths.

9. A method as claimed in any of claims 6-8, wherein the electrically driven beam deflector is an acousto-optical device.

10. A method of perforating cigarettes or cigarette components by means of a laser beam, comprising directing an incident laser beam (which may be continuous or pulsed) at an electrically driven beam deflector and controlling the drive to the deflector to (i) produce multiple beams in sequence along predetermined paths,

(ii) vary the intensity of a beam on at least one of said paths, and (iii) vary the duration of the beam on at least one of said paths.

11. A method as claimed in any preceding claim, wherein an undeflected beam is directed to a heat sink.

12. Apparatus for perforating cigarettes or cigarette components according to the method of any preceding claim, comprising means for supporting a cigarette or cigarette component at a perforation zone, means for directing an incident laser beam, an electrically driven beam deflector arranged in the path of said beam, and control means for controlling the drive of the deflector to cause the beam to be directed in sequence along a plurality of predetermined paths leading to said zone.

13. Apparatus as claimed in claim 12, wherein the control means is arranged to vary the intensity of a beam on at least one of said paths. 8

14. Apparatus as claimed in claim 12 or 13, wherein the control means is arranged to vary the duration of the beam on at least one of said paths.

15. Apparatus as claimed in any of claims 12-14, wherein the electrically driven beam deflector comprises an acousto-optical device.

16. Apparatus as claimed in any of claims 12-15, wherein the control means is arranged to produce multiple beams in sequence along said paths.

17. Apparatus as claimed in any of claims 12-16, wherein the supporting means comprises means for rotating a target cigarette in said perforation zone.

18. Apparatus as claimed in claim 17, wherein said control means is arranged so that said target cigarette is rotated through such angle that it receives at least one substantially complete circumferential row of perforations generated by beams on at least two of said paths.

19. Apparatus as claimed in any of claims 12-18, including optical means defining said predetermined paths and arranged to direct said beams to positions on substantially opposite sides of a target cigarette in said perforation zone.

20. Apparatus as claimed in claim 19, wherein said optical means includes at least one beam reflecting means arranged to reflect the beam on one of said paths but not on any other of said paths.